加藤 直也

症例は72歳男性。C型肝炎を背景に発症した門脈本幹腫瘍塞栓を伴う多発性肝細胞癌(HCC)に対して、大腿動脈アプローチでリザーバーシステムを留置した後に同日より肝動注療法(low dose FP療法)を開始し、一旦退院となった。しかし、治療開始後16日目の外来受診時に血小板数が0.3×10^4/μLと著明な減少を認めたために緊急入院となった。赤血球数、白血球数は正常であり、骨髄穿刺所見もほぼ正常であった。播種性血管内凝固症候群、特発性血小板減少性紫斑病などとの鑑別が問題となったが、ヘパリン起因性血小板減少症(HIT)抗体が陽性であったために、HITを強く疑った。ヘパリンの投与中止およびアルガトロバン20mg/日の投与を開始したが、血小板数の回復がほとんど見られず、ヘパリン化親水性カテーテルも抜去した。その後緩やかに血小板数の上昇を認めたが、HCCの病勢進行を認め、動注療法開始後39日目に永眠された。(著者抄録)

消化器内科医の立場から急性胆嚢炎におけるマネージメントをガイドライン(Tokyo Guidelines 2013)に準拠して述べた。軽症では早期胆嚢摘出術が望ましく胆嚢ドレナージを先行するメリットは少ないので内科から外科へ早急に紹介すべきである。一方、重症は手術リスクが高く、胆嚢ドレナージによるサルベージ療法後に待機的胆嚢摘出術を依頼すべきである。(著者抄録)

Hepatitis C virus (HCV) infection is a major risk factor for developing hepatocellular carcinoma (HCC). The host genetic factors involved in the development of HCC in patients with HCV infection were investigated. To identify the genetic susceptibility factors for HCV-induced HCC, genome wide association studies (GWAS) were conducted in HCV-induced HCC cases and controls of Japanese origin. Single nucleotide polymorphisms (SNPs) which showed possible association in the GWAS were further genotyped using different cohorts. By these analyses, MICA and DEPDC5 SNPs were found to be strongly associated with HCV-induced HCC. These results highlight the importance of MICA and DEPDC5 genetic variations not only as predictive biomarkers for HCV-induced HCC but also as therapeutic targets against hepatocarcinogenesis or HCC.

Recently, first direct acting antiviral (DAA) against hepatitis C virus (HCV) has just approved in Japan. It is a first generation protease inhibitor, telaprevir. Telaprevir inhibits HCV NS3 & 4A serine protease, and combination with pegylated-interferon and ribavirin has now become a standard of care (SOC) for patients with genotype 1 high viral load hepatitis C. Fortunately, more than 50 new antivirals against HCV are under development including antivirals in preclinical trials. New antivirals are classified into several categories; (1) NS3 & 4A protease inhibitor, (2) NS5B polymerase inhibitor, (3) NS5A inhibitor, (4) host factor targeting antivirals, (5) interferon-related antivirals, and others. Combination of different classes of antivirals without interferon is expected to become a future SOC for hepatitis C.

Hepatitis C virus (HCV) core protein, a viral nucleocapsid, has been shown to affect various intracellular events including the nuclear factor kappaB (NF-kappaB) signaling supposedly associated with inflammatory response, cell proliferation, and apoptosis. In order to elucidate the effect of HCV core protein on the NF-kappaB signaling in HeLa and HepG2 cells, a reporter assay was utilized. HCV core protein significantly activated NF-kappaB signaling in a dose-dependent manner not only in HeLa and HepG2 cells transiently transfected with core protein expression plasmid, but also in HeLa cells induced to express core protein under the control of doxycycline. HCV core protein increased the DNA binding affinity of NF-kappaB in the electrophoretic mobility shift assay. Acetyl salicylic acid, an IKK beta -specific inhibitor, and dominant negative form of IKK beta significantly blocked NF-kappaB activation by HCV core protein, suggesting HCV core protein activates the NF-kappaB pathway mainly through IKK beta. Moreover, the dominant negative forms of TRAF2/6 significantly blocked activation of the pathway by HCV core protein, suggesting HCV core protein mimics proinflammatory cytokine activation of the NF-kappaB pathway through TRAF2/6. In fact, HCV core protein activated interleukin-lp promoter mainly through NF-kappaB pathway. Therefore, this function of HCV core protein may play an important role in the inflammatory reaction induced by this hepatotropic virus.

After receiving lamivudine for 3 years to treat chronic hepatitis B, 67-75% of patients develop B-domain L528M, C-domain M552I, or M552V mutations in the HBV polymerase that render hepatitis B virus (HBV) drug-resistant. The aim of this study was to evaluate the influence of these mutations on viral replication and resistance to antiviral agents. We investigated the replication fitness and susceptibility of the wild-type and five mutant HBVs (L528M, M552I, M552V, L528M/M552I, and L528M/M552V) to 11 compounds [lamivudine, adefovir, entecavir (BMS-200475) (+)-BCH-189 (+/-)-FTC (racivir) (-)-FTC (emtricitabine) (+)-FTC, L-D4FC, L-FMAU (clevudine), D-DAPD, and (-)-carbovir] by transfecting HBV DNA into hepatoma cells and monitoring viral products by Southern blotting. The replication competency of the single C-domain mutants M552I and M552V was markedly decreased compared With that of wild-type HBV. However, addition of the B-domain mutation L528M restored replication competence. Only adefovir and entecavir were effective against all five HBV mutants, and higher doses of these compounds were necessary to inhibit the double mutants compared with the single mutants. The B-domain mutation (L528M) of HBV polymerase not only restores the replication competence of C-domain mutants, but also increases resistance to nucleoside analogues.

Hepatitis delta virus infection sometimes causes severe and fulminant hepatitis as a coinfection or superinfection along with the hepatitis B virus. To elucidate the underlying mechanism of injury caused by hepatitis delta virus, we examined whether two isoforms of the hepatitis delta antigen (HDAg) had any effect on five well defined intracellular signal transduction pathways: serum response factor (SRF)-, serum response element (SRE)-, nuclear factor kappaB-, activator protein 1-, and cyclic AMP response element-dependent pathways. Reporter assays revealed that large HDAg (LIDDAg) activated the SRF- and SRE-dependent pathways. In contrast, small HDAg (LHDAg) did not activate any of five pathways. LHDAg enhanced the transcriptional ability of SRF without changing its DNA binding affinity in an electrophoretic mobility shift assay. In addition, LHDAg activated a rat SM22 alpha promoter containing SRF binding site and a human c-fos promoter containing SRE. In conclusion, LHDAg, but not SHDAg, enhances SRF-associated transcriptions. Despite structural similarities be tween the two HDAgs, there are significant differences in their effects on intracellular signal transduction pathways. These results may provide clues that will aid in the clarification of functional differences between LHDAg and SHDAg and the pathogenesis of delta hepatitis.

Hepatitis C virus (HCV) causes a persistent infection, chronic hepatitis, and hepatocellular carcinoma. Since there are several reports indicating that some viruses influence the tumor suppressor p53 function, we determined the effects of MCV proteins on p53 function and its mechanism determined by use of a reporter assay. Among seven HCV proteins investigated (core, NS2, NS3, NS4A, NS4B, NS5A, and NS5B), only core protein augmented the transcriptional activity of p53 and increased the expression of p21(waf1) protein, which is a major target of p53. Core protein increased both DNA-binding affinity of p53 in electrophoretic morbidity shift assay and transcriptional ability of p53 itself in a reporter assay. The direct interaction between core protein and C terminus of p53 was also shown by glutathione S-transferase fusion protein binding assay. In addition, core protein interacted with hTAF(II)28, a component of the transcriptional factor complex in vivo and in vitro. These results suggest that HCV core protein interacts with p53 and modulates p53-dependent promoter activities during HCV infection.

To clarify the effects of hepatitis C virus (HCV) infection on hepatocytes, we analyzed and compared the induction of intracellular signals by HCV and hepatitis B virus (HBV) proteins. We examined the influence of 7 HCV (core, NS2, NS3, NS4A, NS4B, NS5A, and NS5B) and 4 HBV (precore, core, polymerase, and X) proteins on 5 well-defined intracellular signaling pathways associated with cell proliferation, differentiation, and apoptosis by use of a reporter assay. Viral protein-expression vectors were cotransfected into mammalian cells with reporter vectors having a luciferase gene driven by the following inducible cis-enhancer elements: the cyclic adenosine monophosphate response element, the serum response element (SRE), and the binding sites for nuclear factor kappa B (NF-kappa B), activator protein 1 (AP-1), and serum response factor (SRF). In addition, the activation of signals by HCV proteins was examined in a reporter plasmid having a natural interleukin-8 (IL-8) promoter upstream of a luciferase gene. Of 11 HCV and HBV proteins, HCV core had the strongest influence on intracellular signals, especially NF-kappa B-, AP-1-, and SRE-associated pathways. HCV core's activation level exceeded that of HBV X protein, a well-characterized transactivator of these signals. Moreover, HCV core activated the IL-8 promoter through NF-kappa B and AP-1. For the other proteins, HCV NS4B showed signal activation, but signals were activated at a lesser extent. The luciferase reporter assay, a recently introduced technique, helped in the elucidation of molecular events underlying the inflammatory and proliferation process in the liver induced by HCV.

The emergence of resistant hepatitis B virus (HBV), with mutations in the YMDD motif of the polymerase gene after treatment with lamivudine, is becoming an important clinical problem. In this study, susceptibility of wild-type and lamivudine-resistant HBV M552I, M552V, and L528M/M552V mutants to other reverse transcriptase inhibitors was investigated by transient transfection of full-length HBV DNA into human hepatoma cells. HBV DNA replication was monitored by Southern blot hybridization, which showed the presence of a single-stranded band (representative of the HBV replicative intermediates) in the drug-free, wild-type HBV-transfected cells. This band was diminished in the samples of wild-type HBV DNA treated with either lamivudine, adefovir, or lobucavir. The band intensities from the lamivudine-resistant mutants were not decreased by treatment with lamivudine, but were decreased by the treatments with adefovir or lobucavir. In contrast, penciclovir and nevirapine did not diminish the intensity of the single-stranded band of wild-type HBV or the lamivudine-resistant mutants. These results demonstrate that lamivudine-resistant HBV is susceptible to adefovir and lobucavir. Lamivudine-resistant HBV should be treated with adefovir or lobucavir, and combination therapy with lamivudine and adefovir/lobucavir may prevent the emergence of lamivudine-resistant HBV.

Recently, lamivudine used to treat patients with hepatitis B virus (HBV) infection was revealed to have potent antiviral activity. However, HBV resistance to lamivudine has been reported and shown to have amino acid substitutions in the methionine residue of the conserved tyrosine (Y), methionine (M), aspartate (D), aspartate (D) motif of RNA-dependent DNA polymerase. To explore the consequences of substitutions in this motif (YMDD), we made 7 variants by substituting the methionine of the YMDD motif with isoleucine (I), valine (V), alanine (A), leucine (L), lysine (K), arginine (R), and threonine (T). Replication ability of these variants was evaluated by transfection into human hepatoma cells. Sensitivity to lamivudine was tested for replication-competent variants. Four variants with hydrophobic substitutions (I, V, A, and L) remained replication-competent, whereas 3 others with hydrophilic substitutions (K, R, and T) exhibited impaired replication. Of the 4 replication-competent variants, 2 (I and V) were resistant, and 2 (A and L) were sensitive to lamivudine. Because the polymerase and the surface gene overlap, the introduction of these mutations affected the secretion of hepatitis B surface antigen (HBsAg), namely 4 variants (I, V, L, and R) secreted HBsAg, whereas 3 variants (A, K, and T) did not. Our study elucidated that only one amino acid substitution in the YMDD motif was sufficient to cause lamivudine resistance in vitro. As a result of replication competence and lamivudine sensitivity, only viruses having YIDD or YVDD sequences may appear during treatment with lamivudine. This in vitro system could be used to study HBV mutations, replication competence, and their susceptibility to antivirals.

The hepatitis C virus (HCV) nonstructural region 5A (NS5A) protein, without its 146 amino-terminal amino acids and fused to the DNA-binding domain of GAL4, strongly activates transcription in yeast and human hepatoma cells. Transcriptional activation by the HCV NS5A protein may play a role in viral replication and hepatocarcinogenesis.

Hepatocyte related cell lines, namely human embryonic hepatocyte cell line (WRL68) and hepatoblastoma cell line (Hep G2), were tested for their ability to support hepatitis C virus (HCV) replication in vitro. The replicative intermediate of the minus strand HCV RNA was newly transcribed from the inoculated virus, and was stable in WRTL68 cells over a period of 62 days. HCV RNA detected in the culture medium at 62 days after infection suggested a long period of virus secretion from this cell line. In Hep G2, transcription of the minus strand HCV RNA was also detected until 39 days after infection, but transcription and secretion of viral progeny could not be demonstrated. Although HCV infection of WRL68 was not high, this cell line might prove to be a useful tool for studying HCV replication in vitro.

To test whether interferon can prevent acute non-A, non-B hepatitis from becoming chronic, a prospective controlled trial was conducted in 25 patients; 11 were treated for an average of 30 days with a mean of 52 megaunits of interferon and 14 acted as controls. 4 patients in the treatment group who continued to have raised serum aminotransferase concentrations after a year's follow-up were given a second course of interferon. Follow-up at 3 years has revealed that all but 1 of those treated showed normal serum aminotransferase, whereas only 3 controls showed such change (p < 0.02). Serum hepatitis C virus RNA became undetectable in 10 of 11 treated and in only 1 of 12 control patients, which suggests that interferon prevents the progression of acute non-A, non-B hepatitis to chronicity by eradicating HCV.